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Knowledge Base

This Knowledge Base is intended to provide answers to some frequently asked questions and give you some useful tips for using your Hamilton Medical ventilator. If you can't find the information you're looking for here, feel free to mail us with your query.

Incorrect positioning of the CO2 mainstream sensor may affect the quality of the signal. When using INTELLiVENT®-ASV®, an unreliable signal may in turn affect the automated adjustments, as these are dependent on the quality index of the signal from the sensor.

The choice of tube size for uncuffed tubes is commonly made according to Cole`s formula (Age/4 + 4 mm); for cuffed tubes a size 0.5 mm smaller is recommended. The cuff pressure needs to be sufficient to avoid leakage during mechanical ventilation, and also to completely seal the airway and prevent micro-aspiration (thus preventing ventilator-associated pneumonia).

PEEP is used to keep the lung aerated and prevent lung collapse at the end of expiration. However, PEEP may over-distend the normally aerated lung and impair lung perfusion. Therefore, any change in PEEP may affect the overall ventilation/perfusion ratio in an unpredictable way.

The success of NIV depends on the right choice of equipment and adjustment of the settings to suit each individual child. In this Bedside Tip, we show you the initial settings for the most important parameters when applying NIV therapy in children.

My patient is being ventilated in NIV-ST mode and the clinician has ordered PEEP of 5 cmH2O and pressure support of 5 cmH2O. On my Hamilton Medical ventilator the control for adjusting pressure support in NIV-ST is labelled Pinsp (for HAMILTON-G5/S1: Psupport). So what value do I need to set?

A recent physiological study demonstrated that esophageal pressure estimates the pleural pressure at mid-thorax at all levels of PEEP. Therefore, an absolute measurement of esophageal pressure is useful for setting PEEP and monitoring transpulmonary pressure.

The percentage of potentially recruitable lung varies widely among ARDS patients, and zones of collapsed and consolidated alveoli in the most dependent lung frequently require airway opening pressures of more than 35–40 cmH2O to recruit (1).

The expiratory time constant (RCexp) is measured breath-by-breath on all Hamilton Medical ventilators. As RCexp is the product of compliance and resistance, this single variable gives us an overview of the overall respiratory mechanics.

During the expiratory phase of ventilation, the exhaled gas exits the ETT and is measured proximally at the flow sensor. Where a leak is present, the exhaled tidal volume (VTE) is significantly less than the inhaled tidal volume (VTI). In Adaptive Pressure Ventilation (APV) mode, the HAMILTON-G5 must therefore deliver a higher pressure and potentially a larger VTI to compensate for the leak in order to achieve a tidal volume close to the set exhaled volume target (VTarget).

In the presence of dynamic pulmonary hyperinflation, the average end-expiratory pressure inside the alveoli (i.e., the actual, total PEEP (PEEPtot)) is higher than the PEEP applied by the ventilator (PEEPe). The difference between PEEPtot and PEEPe corresponds with the intrinsic PEEP (PEEPi), and is also known as AutoPEEP (1).

Most ventilator manufacturers use their own specific abbreviations for the different ventilation modes on their ventilators. It is important for users to have a tool that enables them to compare the modes of one manufacturer with the modes of another.

Optimal patient-ventilator synchrony is of prime importance, as asynchronies lead to increased work of breathing and patient discomfort, and are also associated with higher mortality and prolonged mechanical ventilation (1, 2, 3).

Ventilators from Hamilton Medical offer the volume-targeted modes APVcmv/APVsimv (Adaptive Pressure Ventilation) as an alternative Time-Cycled Pressure Limited (TCPL) and Pressure-Controlled Ventilation (PCV) for neonates. There is strong evidence in the literature for the use of volume-targeted ventilation in neonates (see references below).

High flow oxygen therapy combines several physiological effects: Oxygenation, PEEP, an increase in the end-expiratory lung volume (EELV), a lower respiratory rate (RR), a decrease in intrinsic PEEP and work of breathing, lower PaCO2, and improved humidification and comfort (1, 2). The optimal flow setting depends on the indications and the desired physiological effect.

By knowing how CO2 behaves on its way from the bloodstream through the alveoli to the ambient air, you can obtain useful information about ventilation and perfusion. Monitoring the CO2 level during respiration (capnography) is noninvasive, easy to do, and relatively inexpensive.

One of the greatest challenges when mechanically ventilating patients is finding the correct setting for positive end-expiratory pressure (PEEP). This task can be made easier by using transpulmonary pressure measurement to distinguish between the pressure in the lungs and the chest wall components.

In conventional ventilation modes, the clinician sets ventilator controls such as tidal volume, respiratory rate, and expiratory and inspiratory time to achieve clinical targets, including a certain level of oxygenation and alveolar ventilation for the patient.

Airway driving pressure is associated with clinical outcomes in ARDS, post-surgical, and normal-lung patients, and is a measure of the strain applied to the respiratory system and the risk of ventilator-induced lung injuries. Evidence suggests we should keep driving pressure below 14 cmH2O. But how can we measure it?

The American Thoracic Society and the American College of Chest Physicians recently provided recommendations to help optimize liberation from mechanical ventilation in adult ICU patients (1). They suggest using a ventilator liberation protocol and performing spontaneous breathing trials (SBTs) with modest inspiratory pressure support (5-8 cmH2O). So how do we implement these recommendations using the Adaptive Support Ventilation (ASV) mode?

Even if the idea of a “safe” plateau pressure is already being questioned, it is still standard of care to use it for tailoring lung-protective ventilation in acute respiratory distress (ARDS) patients1. This gives rise to a common question asked by users of HAMILTON-C1/T1/MR1 ventilators: How can I measure/calculate Pplateau with my device?

The table displayed here, which is included with all the relevant consumables sold, shows the various sizes of bonnets, prongs and masks, and the corresponding recommended head circumferences and weights.